This invention relates in general to apparatus for mixing gases and liquids to dissolve the gas in the liquid and, more particularly, to apparatus for mixing ozone into water as part of a water purification system.
Ozone and mixtures of ozone and oxygen have long been mixed with water or other liquids to eliminate contaminants, in particular bacterial contaminants. Ozone is typically generated by exposing oxygen to a corona discharge unit. The ozone-oxygen gas mixture is then introduced into the liquid to be treated in the form of small bubbles. Typical contact and mixing chambers incorporate a venturi mixer or inductor port to inject ozone and oxygen (or, if desired, air in place of oxygen) into a fluid stream of water or other suitable liquid by venturi suction or high pressure injection.
In conventional ozone contact chambers, the ozone gas bubbles are injected at the base of a tall liquid column. The ozone-oxygen bubbles float to the surface slowly, their upward movement slowed by the downward counter flow of the liquid stream. To achieve sufficient contact time before the liquid passes from the mixing column, the column must be extremely tall and is difficult to install in ordinary sized plant equipment rooms. The concentration of dissolved ozone-oxygen is undesirably diluted in the larger vertical columns.
Ozone is also useful in water purification systems and the like to aid in removing small organic particles. Ozone causes a flocculating effect which improves the ability of a downstream filter to remove particles which would ordinarily pass through the filter. Highly uniform mixing of a carefully selected proportion of ozone is necessary, since an excess of ozone may break up organic particles, allowing the smaller particles to pass through the filter.
Thus, there is a continuing need for improved apparatus for more completely and uniformly mixing a gas, such as ozone, with a liquid, such as water, and for mixing the gas with the liquid in precise and controlled proportions of gas to liquid.